page_title: Mycoplasma pneumoniae
section_title: Cell biology
hierarchical_section_title: Mycoplasma pneumoniae / Cell biology
caption_attribution_description: English: "A, scanning electron microscopy of filamentous M. pneumoniae. B, transmission electron microscopy of flask-shaped M. pneumoniae (M) attached by the terminal tip organelle (arrow) to ciliated mucosal cells. Magnification: A, x10,000;B, x36,000."
context_page_description: Mycoplasma pneumoniae is a very small bacterium in the class Mollicutes.
  It is a human pathogen that causes the disease mycoplasma pneumonia, a form of atypical bacterial pneumonia related to cold agglutinin disease. M. pneumoniae is characterized by the absence of a peptidoglycan cell wall and resulting resistance to many antibacterial agents. The persistence of M. pneumoniae infections even after treatment is associated with its ability to mimic host cell surface composition.
context_section_description: Mycoplasmas, are among the smallest self-replicating organisms, are parasitic species that lack a cell wall and periplasmic space, have reduced genomes, and limited metabolic activity. Mycoplasma pneumoniae cells have an elongated shape that is approximately 0.1–0.2 µm (100-200 nm) in width and 1-2 µm (1000-2000 nm) in length. The extremely small cell size means they are incapable of being examined by light microscopy; a stereomicroscope is required for viewing the morphology of M. pneumoniae colonies, which are usually less than 100 µm in length. The inability to synthesize a peptidoglycan cell wall is due to the absence of genes encoding its formation and results in an increased importance in maintenance of osmotic stability to avoid desiccation. The lack of a cell wall also calls for increased support of the cell membrane(reinforced with sterols), which includes a rigid cytoskeleton composed of an intricate protein network and, potentially, an extracellular capsule to facilitate adherence to the host cell. M. pneumoniae are the only bacterial cells that possess cholesterol in their cell membrane (obtained from the host) and possess more genes that encode for membrane lipoprotein variations than other mycoplasmas, which are thought to be associated with its parasitic lifestyle. M. pneumoniae cells also possess an attachment organelle, which is used in the gliding motility of the organism by an unknown mechanism.
caption: A) Filamentous Mycoplasma pneumoniae cells B) M. pneumoniae cells (M) attached to ciliated mucosal cells by the attachment organelle (indicated by arrow)
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